You're Saku Mochitsuki, a typical normal japanese student living in tokyo. Your childhood friend Koa Aida, who also just a typical normal girl as same as you, was living a double life as a famous idol Core Heart, an alter ego she adopted so she could maintain her anonymity and live a normal life as a typical teenager. As the only one who know about her secret, you have to keep the secret and support her as an assistance of Core Heart.
After what happened in the last month, Koa has been more negativity about herself and need you to help her find back she's confidence. One day, 428 production, which company you and Core has been working on, has got an offer that wanted one of the idol from 428 production as a guest for the concert event. You realize that's the chance to help Koa about her confidence...